REPORT ON VARIOUS METHODS FOR DESTROYING SCALE 
INSECTS. 
By D. W. CoquiLLert, Special Agent. 
LETTER OF SUBMITTAL. 
Los ANGELES, CAL., October 8, 1890. 
Sir: I herewith submit my annual report for the season of 1890. The Australian 
lady-bird (Vedatia cardinalis Mulsant) recently introduced by this Division, success- 
fully survived the winter unprotected out of doors, and as early as the month of 
March I was able to distribute several colonies to those requesting them. Lest this 
species, after exterminating the Fluted or Cottony-cushion Seale (Icerya purchasi 
Maskell) should become extinct on this coast, our State Board of Horticulture, at the 
suggestion of its president, Hon. Ellwood Cooper, has erected two propagating 
houses over two large orange trees belonging to Col. J. R. Dobbins, in the San Ga- 
briel Valley ; in these houses the Vedalias are to be propagated and distributed to 
those requiring them. At the present writing it is no easy matter to find a single 
living Icerya anywhere in this part of the State, although in the early part of the 
season they appeared in limited numbers in a great many places; later in the season 
the Vedalias also appeared in considerable numbers, and by sending colonies of these 
to the different localities where the Iceryas had appeared, the latter were effectually 
held in check. 
The Red Scale (Aspidiotus awrantii Maskell), so destructive to Citrus trees in certain 
jocalities, is rapidly reduced in numbers through the agency of the treatment with 
hydrocyanic acid gas, described in my previousreports. This treatment is now being 
largely used for the above mentioned purpose, and is giving far better results than 
have ever been obtained by the use of any kind of a spray ; numerous instances have 
occurred where, upon large Citrus trees treated with this gas, neither myself nor other 
parties were able to find a single living Red Scale, either upon the bark, leaves, or 
fruit—a result which so far as I am aware has never been obtained by the use of any 
kind of aspray. The cost of treating trees with the gas is scarcely greater than that 
of using a spray, while the method has been so greatly simplified that trees can now 
be treated with the gas very nearly as rapidly as they can be sprayed. Ihave not as 
yet learned that any person, or even a single domestic animal, has ever been acci- 
dentally injured either by the gas itself or by the materials used in producing it. All 
of the objections which at first were urged against the use of this gas—the danger of 
being poisoned by it or by the chemicals used, the great expense attached to its use, 
and the impracticability of operating the tents—have finally been overcome, and the 
treatment is now in successful operation. 
In my last report I gave an account of the spraying of a number of orange trees 
at Orange according to instructions. These trees were not again sprayed until the 
lapse of a little over one year, At this latter date the trees were again badly infested 
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